WEBVTT - How Does Salt Prevent Food Spoilage? 0:00:02.040 --> 0:00:07.320 Welcome to brain stuff from how stuff works. Hey, brain stuff, 0:00:07.400 --> 0:00:10.680 Lauren Vogel bomb. Here, let's talk salt. You might toss 0:00:10.680 --> 0:00:13.120 a little over your left shoulder for good luck, sprinkle 0:00:13.160 --> 0:00:15.240 some on your eggs, or even tip a shaker into 0:00:15.280 --> 0:00:18.480 a frothy beer. However you use it, one thing's for certain. 0:00:18.600 --> 0:00:21.840 Most of us take salt for granted. Salt wasn't always 0:00:21.880 --> 0:00:24.720 such a simple matter. For centuries, it was a rare commodity, 0:00:24.800 --> 0:00:27.800 used as payment, as an impetus for wars, and often 0:00:27.840 --> 0:00:31.840 for survival. Salt preserved fish and ancient Egypt seasoned Roman 0:00:31.880 --> 0:00:34.600 salad dressings, and even came to stand for a measure 0:00:34.600 --> 0:00:37.880 of a person's integrity. A competent Roman soldier was worth 0:00:37.960 --> 0:00:40.800 his salt. He had earned his allowance of the valuable seasoning. 0:00:41.240 --> 0:00:44.879 But more than being tasty, salt kept entire civilizations alive 0:00:44.960 --> 0:00:47.520 thanks to its ability to prevent foods from turning into 0:00:47.760 --> 0:00:52.760 bacterial Latin killers. To understand how salt prevents foods from spoiling, 0:00:52.880 --> 0:00:56.160 it's important to first grasp how it's used to preserve foods. 0:00:56.520 --> 0:00:59.480 Salt is used in two primary ways, either in granual 0:00:59.560 --> 0:01:02.360 form or in brine form. A brine being a water 0:01:02.440 --> 0:01:05.440 and salt solution. A ham, for example, might be cured 0:01:05.440 --> 0:01:08.720 with salt, and cucumbers are preserved and turned into pickles 0:01:08.840 --> 0:01:12.400 with brine. Curing with salt granules, known as dry curing, 0:01:12.640 --> 0:01:14.880 means applying salt to the outside of a cut of 0:01:14.880 --> 0:01:17.039 meat and storing it for a couple of days up 0:01:17.080 --> 0:01:19.600 to several weeks. It's one of the most ancient ways 0:01:19.640 --> 0:01:22.520 of curing meats. Modern curing can involve injecting meat with 0:01:22.600 --> 0:01:25.600 salt brine. Whatever the form of salt it's used, the 0:01:25.640 --> 0:01:28.280 mineral preserves foods and makes them safer to eat by 0:01:28.280 --> 0:01:31.880 preventing bacteria from growing, including the bacteria that break down 0:01:31.920 --> 0:01:35.080 rotting food, and also food board pathogens such as salmonella, 0:01:35.240 --> 0:01:38.920 which can cause food poisoning, typhoid fever, and other serious problems. 0:01:39.480 --> 0:01:42.520 Salt inhibits bacteria in a variety of ways. It's a 0:01:42.600 --> 0:01:45.959 disruptor that reeks havoc in microbes, interrupting their enzymes and 0:01:46.160 --> 0:01:49.800 chipping away at their DNA. It most often works through dehydration, 0:01:49.880 --> 0:01:52.840 though removing many of the water molecules the bacteria need 0:01:52.920 --> 0:01:55.960 to live and grow. Water molecules and food are measured 0:01:56.000 --> 0:01:59.480 in terms of product water activity, a number that signifies 0:01:59.560 --> 0:02:03.440 the free water molecules present before salt preservation. Many fresh 0:02:03.440 --> 0:02:07.120 foods have point nine nine product water activity. The product 0:02:07.120 --> 0:02:10.040 water activity is lowered when salt dehydrates the food through 0:02:10.080 --> 0:02:13.160 the process of lasmosis. In essence, the salt around the 0:02:13.160 --> 0:02:16.720 outside of the food draws water molecules out and replaces 0:02:16.760 --> 0:02:19.600 them with salt molecules until the amount of salt is 0:02:19.600 --> 0:02:23.200 equal inside and out, Lowering the water product activity to 0:02:23.440 --> 0:02:26.639 point nine ford to point nine one is usually sufficient 0:02:26.680 --> 0:02:35.600 to prevent most bacterial growth. Today's episode was written by 0:02:35.639 --> 0:02:38.600 Laurie L. Dove and produced by Tristan McNeil. For more 0:02:38.600 --> 0:02:41.320 on this and tons of other salty topics, visit our 0:02:41.440 --> 0:02:54.200 home planet, how stuff works dot com.